i BYZANTINE CHURCHES Government and to the late Sir Nicholas O*Conor, British Ambassador at Constantinople, for permission to make a scientific examination of the churches of the city. To the present British Ambassador, Sir Gerard Lowther, best thanks are due for the facilities enjoyed in the study of the church of S. Irene. I have been exceedingly fortunate in the architects who have given me the benefit of their professional knowledge and skill in the execution of my task, and I beg that their share in this work should be recognized and appreciated as fully as it deserves. To the generosity of the British School at Athens I am indebted for being able to secure the services of Mr. Ramsay Traqualr, Associate of the Royal Institute of British Architects and Lecturer on Architecture at the College of Art in Edinburgh. Mr. Traquair spent three months in Constantinople for the express purpose of collecting the materials for the plans5 illustrations, and notes he has contributed to this work. The chapter on Byzantine Architecture is entirely from his pen. He has also described the architectural features of most of the churches ; but I have occasionally introduced information from other sources, or given my own personal observations. I am likewise under deep obligation to Mr. A. E. Henderson, F.S.A., for the generous kindness with which he has allowed me to reproduce his masterly plans of the churches of SS. Sergius and Bacchus, S. Mary Panachrantos, and many of his photographs and drawings of other churches in the city. I am, moreover, indebted to the Byzantine Research and Publication Fund for courteous permission to present here some of the results of the splendid work done by Mr. W. S. George, F.S.A., under unique circumstances.